Hydraulic press



1947. J. 1.. LEFLER 2,413,876

HYDRAULIC PRESS I Filed July 12, 1945 a l N N INVENTOR. JAMES L. LEFLERBY i u D ATTORNEY Patented Jan. 7 1947 HYDRAULIC v v Jarn es L. Lefler,North Hollywood, Calif; ass gnor to Bendix Aviation Corporation, SouthBend,

1nd,, acorporation ofQDelawar-e Application July 12, 1945, Serial No.604,629

, v 1 This invention relates is particularly useful in hand-operatedpresses;

An object of the invention is to provide an in expensive, economicalpress for use in operations requiring the development of large forcesapplied through relatively short distances.

Another object is to provide aipress that utilizes" an ordinary sourceof compressed air forefiecting large movements of the press where smallforces are involved while utilizing high pressure by draulic fluid forthe developmentof large forces acting through only short distances; iOrdinary hydraulic presses require 'a power pump of substantial capacityfor moving the press at a reasonable speed while at the same timedeveloping the desired high forces. Because of the expenseof-power-pumping equipment; the use of hydraulic presses had beenlimited to situations .where there was a substantial amount of presswork to be done. For manypur'poses, it is only to hydraulic' 'pressesand1 m c v There is shown in the diagram a conventional press I consistingof frame vertical members 2 supporting a table 3 on which a work-piecemay be placed;- and supportin above the table 3 a hydraulic ram cylinderbcontaining a piston 5 having a stem 6 which'extends through the bottomof the cylinder and can be moved toward the table 3 to bear against aworks-piece thereon.

The upper end of theycylinder 4 above the piston 5 is connected to afluidline 1,, and the lower end of the cylinder below the ,piston 5 isconnected to an air line 8. The upperend of the piston is at all timesfilled with hydraulic fluid,

hereinafter referred to-as oil;

The oil line 1 connects to a control valve I I and also to the dischargeport I2 of a hand pump I3.

. This hand pump comprises a relatively small -\necessary to develophigh fluid pressures in a s hydraulic press during final movement of thepress, and a fluid pressure as large as may be required can be developedwith a relatively small and economical hand pump by making the pumppiston relatively small; However, when the pump piston is made small todevelop the desired high pressure, its volumetric capacity iscorrespond- ,lngly reduced so that it may require a great deal of timeto move the press platen into position where it bears against thework-piece.

I ,1 accordance with the present inv 'ntion, I pro ide a press that iscapable of develoriing high forces and, at the same time, is capableofrapid movement up to the point where the gh force must be generated, byproviding a sma 1 capacity high pressure hand pump, in combination withmeans utilizing an ordinary source of compressed air for moving thepress rapidly so long as only low forces are involved. Thearrangement-is such that only a single ram is employed on the press andonly hydraulic fluid is introduced 'i nto the working chamber of} thepress ram, the fluid being circulated to and from the ram by {airpressure during rapid movement of the-press to engage and disengage awork-piece.

The manner in w ich the foregoing objects are attained, together, ithother more specific ob- I jects and features" of the invention, will beapparent from the following detailed description of a preferredembodiment of the invention which refers to the drawing.

The single figure of the drawing is a schematic diagram of a system inaccordance withrthp invention. I.

diameter. working cylinder I4 containing a piston I5 adapted to bereciprocated by a handle IS. The cylinder I4 is connected to thedischarge port I2 past a check valve I6 and to an inlet port I8 past acheck valve ll; the latter port being. connected by a line 20 to theupperend of a cylinder 2| and to the valve II. The lower end ofcylinder2I is connected by an air line 22 to the valve II. 1 Anyordinary source of compressed air 23 :is connected. by a line to thevalve I I.

The cylinder 2| contains a floating piston 25 which servesto maintainoil in the upper end of the cylinder separated from air'in the lowerpart.

The systemdescribed operates as follows:

When it is desired to elevate the piston 5 of the rain, the valve II isrocked clockwise into the dotteddine position labeled Up. This connectsthe line 24 from the pressure air supply to the line 8 leading to thelower end of the ram cylinder so that pressure of the compressed air isapplied to raise the ram piston. At the same time, oil in the upper endof. the ram cylinder flows out through the line I and through the valveI I to the line 20 and into the upper end of the displacement cylinder2|. This moves the piston 25 downwardly, and the air in the lower end ofcylinder 2| is exhausted to atmosphere through line 22, valve II and anexhaust port 21 in the valve.

When it is desired to lower the piston 5 of I the ram, the control valveII is rocked counterclockwise into'the dotted line positionmarked"Down.? In this position, it admits pressure air from line 24 throughline 22 to the lower end of the displacement cylinder 2|, forcing thepiston 25 upwardly to displace oil from the upper end of the cylinderthrough the line 20, and a check valve 28 and the line I into the upperend of the ram cylinder. At the same time, the lower end of the ramcylinder is connected through line,

has contacted a work-piece positioned in'the f press. However, theoperator can thereafter build up the pressure in the upper end of theram cylinder to any desired value by reciprocating the handle l6 of thehand pump. On each outward stroke of the piston I5, it draws in oil fromthe upper end of cylinder 2| through the pipe 20 past the inlet checkvalve H, and on each inward" stroke forces such oil past the outletcheck valve l6 and directly through the line 1 into the upper end of theram cylinder.

The operator can leave the valve II in the -Down position or return itto Neutral position, and the hand pump will be equallyefiective. 7

After the pressing operation has been completed, the operator can againraise the rampisconnected to the bottom of cylinder 2|, and the air line22 should beconnected to the top of the cylinder. It is usuallydesirable to provide a barrier between the air and the oil within thedisplacement cylinder to prevent mixing of the air in the oil underpressure.

It is common practice in accumulators for hydraulic systems to emtionedcan'be made while still utilizing the invention, which is to be limitedonly to the extent set forth in the appended claim.

A hydraulic press comprising: a ram cylinder containing a piston adaptedto be reciprocated in one direction to press a work-piece. and in theopposite direction to releasethework-piece, said ram cylinder having aliquid opening in one end for receiving liquid to move the piston insaid one direction and an air opening in the other end, a source ofcompressed air under medium pressure, aclosed reservoir for hydraulicliquid and air and having aliquid opening and an air opening,ahigh-pressure, low volumetric capacity pump having an inlet opening andan outlet opening, said pump being adapted to develop pressures muchgreater than the pressure of said air source, check valve meansinterconnecting said liquid openings of said ram cylinder and reservoirfor permitting flow from said reservoir to'the ram cylinder, whilepreventing reverse flow,.a control valve having first, second, and thirdposition'sand connections extending from said ram cylinder, said airsource, said reservoir,v ands'aid pump to said valve; said valve when insaid first position connecting the liquid opening of said reservoir totheliquidopening of said .ram, connecting said air source to the airopening of the ram cylinder,

andconnecting the air opening ofsaid reservoir to atmosphere, wherebysaid ram piston is moved in said other direction and liquid in the ramcylinder is returned to said reservoir; said valve when in said secondpositionconnecting said air source to the air opening, ofsaid reservoir,and connecting the airopening of said ram cylinder to exhaust,whereby-liquid is displaced from said reservoir, through said checkvalve means into ploy either a solid piston or a flexible diaphragm or aflexible bladder to prevent mixing of the oil and the air, and aflexible diaphragm or bladder may be employed in place of the floatingpiston 25 if desired. In such instances, it is not necessary that thedisplacement reservoir be in a form of a cylinder, and it mayconveniently be in theform of a sphere, similar to conventionalhydraulic accumulators.

Although for the purpose of explaining the invention, a specificembodiment has been described, various departures other than those men-,theram cylinder to move the ram piston in said one direction with lowforce; said valve, when in said third position, connecting. the airopenings of said ram cylinder and reservoir to exhaust;

, and means connecting the liquid opening of the JAMES L.

